Submarine cable overcurrent protective device



Sept. 16, 1952 P. H. WELLS Er AL.

SUBMARINE CABLE OVERCURRENT PROTECTIVE DEVICE Filed May 51 1951 AC SOURCE INVENTORS P H WELLS BY C. H. CRAMER ATT RNEY Patented Sept. 16, 1952 UNITED STATES PATENT OFFICE SUBMARINE CABLE OVERCURRENT PROTECTIVE DEVICE Application May 31, 1951, Serial No. 229,195

The present invention relates to submarine cables and more particularly to submarine cables having repeating amplifiers incorporated therein.

As described in the copending patent application of H. F. Wilder, Serial No. 229,146, filed May 31, 1951, inclusion of a repeating amplifier in a remote portion of a submarine cable circuit provides many advantages, such as a large increase in the speed of telegraphic communication over the cable.

Since a repeating amplifier in a submarine cable circuit will be located a consideiable distance from a terminal station and since such an ampliiier will generally be located in a submerged portion of the cable, it is necessary to supply ampliiier operating power thereto from a shore station. For stable repeating amplifier operation, it is desirable that the operating current for the amplifier be maintained substantially constant. This latter condition is diiilcult to achieve in practice because of the presence of earth potentials induced in the cable circuit and which may be of positive or negative polarity. These earth potentials may have values of from to 300 or more volts and may, in some instances, produce currents in the cable circuit sufficiently large to damage the cable.

In the copendingpatent application of Philip I-I; Wells et al., Serial No. 229,194, filed May 3l, 1951, there is illustrated a power supply for use with a submerged repeater and inwhich the current supplied to a repeating ampliiier is maintained substantially constant over a wide range of variations in earth potentials and commercial alternating current voltage."

Since a submarine cable may be seriously damaged if the current therethrough becomes excessive, and since the control range of the current and voltage control circuits may be exceeded, it is desirable that an overcurrent pro'- tective device be provided to open the power supply and insert impedance in series with the cable when the current therethrough exceeds a predetermined value.

Accordingly, it is an object of the invention to provide an overcurrent protective device for a submarine cable.

More particularly, it is an object of the invention to provide an overcurrent protective device for a submarine cable having a repeating amplifier incorporated in an intermediate portion thereof which will open the l repeating amplifier power supply circuit and in sert impedance in series with the cablewhen the current therethroughv exceeds a,predetermined value. e

1o claims. (o1. 17e-se) Another object of the invention is to provide an overcurrent protective device of the above type, wherein operating personnel may not restore the cable to service without adequate protection aaginst a continued existence of the dangerous condition.

Further, objects of the invention will appear from the following description.

In accordance with the invention, these objects are achieved by providing means responsive to an excess current flow in the cable circuit to disable the power supply, to interpose a protective impedance element in the cable circuit and to provide an alarm indication to operating personnel, and manually operable means, operable solely when the power supply is adjusted to deliver a minimum current, to render the power supply operative and to remove the protective impedance element from the cable circuit.

The invention will now be described in greater detail with reference to the appended drawing in which there is illustrated one embodiment of the overcurrent protective device according to the invention.

Referring now to the drawing, power from an alternating current source is applied to a controlled rectifier l0 through a transformer Il. The negative terminal of rectifier l0 is connected to the apex of a cable bridge l2 through a conductor I3. One arm of cable bridge I2 is coupled to a conductor I4 of submarine cable l5 through series connected resistors 'R andRS. The other arm of cable bridge l2 is coupled to ground through an artificial line I8. The positive terminal of rectifier lil is coupled to ground through an absorption type regulator Il. Negative polarity is applied to cable conductor i4 to minimize electrolytic effects at the casing of a repeating amplifier A interposed in cable l5 in a submerged portion thereof. Earth potentials,

'which vary in magnitude and polarity, are repet al. referred to hereinbefore. itis to be'underfv stood that the invention is not limited to use with 3 the power supply described in the said application of Philip H. Wells et al., but is equally applicable to any power supply suitable for supplying a remote repeating amplier included in a submarine cable circuit.

When the'cable eurrent exceeds a predetermined maximum value, the voltage drop across resistor R becomes suflicient to energize a principal winding of relay LI, winding 26 being shunted across resistor R. Energization of winding. 20 causes normally open contacts 2| to close. Once closed, contacts 2| will not reopen upon deenergization of Winding 20. To reopen contacts 2|, reset Winding 22 of relay Ll must loeA energized. Closing of contacts 2| completes an energizing circuit for principalY winding 23 of a relay L2 from positive battery through resistor 24, contacts 2| and winding 23 to ground. Energization of winding 23 causes armatures 25 and 26 to break with back contacts 21 and 28, respectively, and to make with front contacts 29 and 30, respectively.4 Once armatures 25 and 26 are made witncontacts 29 and 30, respectively, they will not return to contacts 21 and 28, respectively, until a reset Winding 3| of relay L2 is energized.

In the normal positions of armatures 25 and 26, circuits are completed from positive battery through armature'25, contact 21 and relayL3 to ground and from positive battery through armature 26, contact 28 and relayL4 to ground. Normally closedV contacts 32 of relay L3 are included in the primary side of transformer so that deenergization ofrelayLS will open the supply circuit for rectifier l0. Normally closed contacts 33 o freiay L4 are arranged to short resistor RS out of the cable circuit, so that deenergization of relay L4 will place resistor RS in the 4cable circuit as a protective resistor. Since contacts -33 normally carry the relatively large repeater current and the signal current, it is desirable that contacts 33 provide a minimum resistance in the, cable circuit. Relay L4 is, therefore, preferably realized as a mercury relay.

When relay windingl 23Y is energized, circuits are completed from." positive battery through armature 25, contact 29, lamp 34 and resistor 35 to ground and from positive battery through armature 26, contact 30. Winding 36 of a differential relay L5, slowV acting relay L6 and resistor 31 to ground.

Lamp 34 provides a. visual indicationY oi an overcurrent condition in the cablev current to operatirlfr personnel. Unlike the audible alarm to be described hereinafter, lamp 34 remains energized until the cable circuit, is ready to be restored to operation.

Energization of Winding 36 or `relay L5 closes normallyv Open contacts 38, thereby closing a circuit from positive battery through contacts 38 and alarm circuit 39 to ground to provide an audible indication of an overcurrent condition in the cable circuit tooperating personnel. Energization of winding 36 also opens normally closed contacts 40. When slow acting relay L6 operates, normally open contacts 4| thereof close.

When an attendant presses button KI, a circuit is completed from positive battery through armature 26, contact 30, Winding 42 of relay L5, resistor 43 and normally open contacts 44 to ground. Winding 42 is Wound vin opposition to winding 36 and energization of winding'42 -Will cause contacts 4|!l tor'eturn to' their normally- 4 closed condition and contacts 38 to return to their normally open condition. The opening of contacts 38 will open the energizing circuit for alarm 39. Closing of contacts 46 will complete a locking circuit for winding 42 extending from positive battery through armature 25, contact 30, winding 42, resistor '43, contacts 40 and contacts 4| to ground. Accordingly, alarm 39 will remain deenergized after release of button K| because winding 42 of relay L5 will remain energized through its locking circuit.

For placing the power supply circuit back in operation, there provided a switch 45 having Y a pair of contacts 46 and 41 normally open with respect to a pair o rftongues 48 and 49, respectively. Tongues 48` and 49 are made with contacts 46 and 41, respectively, when an attendant presses a button K2. When button K2 is pressed. an energizing circuit for reset winding 22 of relay L| is completed from positive battery through tongue 48 contact lli and Winding 22 to ground. Energization of Winding Z2 opens con.- taots 2|, thereby removing battery irom Windring 23 of relay L2 Pressing button Kjwill also close an energizing circuit for reset Winding 3l of relay L2 from nositivebottcry through tongueV 49. contact 4l, winding, 3l. tno parallel combination of a copacitori and a resistor; 5l aminormally open contacts 53 to ground. Energiea-` tion of Winding 3| causes armatures 25 and 26 to break with contactsy 2 9 and 3Q, respectively, and to make with contacts 21 and 28, thereby energizing relays L3 and'IAf. Energization of relayV tacts 53 are closed by an extensionv 5,4 of asliiierY 55. of a current control potentiometer 56. Ex-l tension 54 closes contacts 53011151 when. slider 55 adjusts potentiometer 56 to-maximum resistance. circuit to current controlled stabilizer-QS, it adjusts stabilizer CS toprovide'minimum currentv from rectifier l0.' Adjustment of sliderv 55 to. the minimum current position is a conditionv precedent to energization of lwinding 3| and hence insures thatthe cable circuit will be protected from damage which could occur, it, fulll current were returned theretolwth a continued` abnormal earth potential condition.

If a device were provided for. varying the voltage applied to rectifier l0, switch 53, could conveniently be arranged to. close ,only on a minimum voltage setting', thereby providingsnbstantially thc some protection as thcarranecincnt illuS# trated. 4

Further protection against a continued abnormal earth current condition is provided by capacitor 59, which is shunted by v.high resistance 5l. Current will now through capacitor 50Y only` until it is charged, at which time 'the energiaing;y circuit for winding 3| will be opened.V Accordingly, continued depression of button'KZv will not` maintain energization o f relaysY L3 and L4 ifthe current through resistor R is in excess ofmthe predetermined maximum safe value. 1f Vthe abnorinal earth potential condition has cleared,` the circuit will return to normal upon depression ofV button K2 andthe cable current can be adjusted.

to the proper value by adjusting slider 55.

Since potentiometer 56 is in the inputv It will be evident that the cable will be protected from excessive earth currents in the event of a station power failure because such a failure will automatically deenergize relays L3 and L4, placing the cable in its protected condition.

While the invention has been described in a particular use thereof and in a particular embodiment, it is not desired that it be limited thereto, for obvious modifications thereof will occur to those skilled in the art without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is: V

1. In a terminal station for a submarine cable circuit having a repeating amplifier interposed in a portion thereof remote from said station, the combination comprising a source of direct current power for said amplifier, a control circuit coupled to said source to control the magnitude of the current delivered therefrom, a first impedance element intercoupling said source and said cable circuit, and an overcurrent protection device comprising means selectively to disable said source, a second impedance element, circuit means selectively to interpose said second impedance element in said cable circuit, means responsive to a fiow of current through said first impedance element in excess of a predetermined maximum value to actuate said disabling means and said circuit means thereby to disable said L source and to interpose said second impedance element in said cable circuit, first manually operable means coupled to said control circuit to adjust said control circuit for a predetermined minimum current flow from said source, second manually operable means to actuate said disabling means and said circuit means thereby to render said source operative and to remove said second impedance element from said cable circuit and means coupled to said second manually operable means and arranged to permit operation thereof solely when said control circuit is adjusted for said predetermined minimum current flow from said source.

2. In a terminal station for a submarine cable circuit having a repeating amplifier interposed in a -submerged portion thereof and being subjected to varying earth potentials, the combination comprising a source of direct current power for said amplifier, a control circuit coupled to said source to control the magnitude of the current delivered therefrom, a first resistance element intercoupling said source and said cable circuit, and an overcurrent protection device comprising means selectively to disable said source, a second resistance element, circuit means selectively to interpose said second resistance element in said cable circuit, means responsive to a flow of current through said first resistance element in excess of a predetermined maximum value to actuate said disabling means and said circuit means thereby to disable said source and to interpose said second resistance element in said cable circuit, first manually operable means coupled to said control circuit to adjust said control circuit for minimum current flow from said source, second manually operable means to actuate said disabling means and said circuit means thereby to render said source operative and to remove said second resistance element from said cable circuit and means coupled to said second manually operable means and arranged to permit operation thereof solely when said control circuit is adjusted for minimum current ow from said source. Y

3. In a terminal station for a submarne cable circuit having a repeating amplifier interposed in a portion thereof remote from said station, the combination comprising a source of direct current power for said amplifier, a control circuit coupled to said source to control the magnitude of the current delivered therefrom, a first impedance element intercoupling said source and said cable circuit, and an overcurrent protection device comprising first relay means selectively to disable said source, a second impedance element, second relay means selectively to interpose said second impedance element in said cable circuit, third relay means responsive to a flow of current through said first impedance element in excess of a predetermined maximum value to actuate said first relay means and said second relay1 means thereby to disable said source and to interpose said second impedance element in said cable circuit, first manually operable means coupled to said control circuit to adjust said control circuit for minimum current flow from said source, second manually operable means to actuate said third relay means thereby to actuate said first and second relay means and to render said source operative and to remove said second impedance element from said cable circuit and circuit means coupled to said third relay means and arranged to permit operation thereof solely when said control circuit is adjusted for minimum curn rent flow from said source.

4. In a terminal station for a submarine cable circuit having a repeating amplifier interposed in a portion thereof remote from said station, the combination comprising a source of direct current power for said amplifier, a control circuit coupled to said source to control the magnitude of the current delivered therefrom, a first impedance element intercoupling said source and said cable circuit, and an overcurrent protection device comprising means selectively to disable said source, a second impedance element, circuit means selectively to interpose said second impedance element in said cable circuit, means responsive to a flow of current through said lfirst impedance element in excess of a predetermined maximum value to actuate said disabling means and said circuit means thereby to disable said source and to interpose said second impedance element in said cable circuit, first manually op erable means coupled to said control circuit to adjust said control circuit for minimum current iiow from said source, second manually operable means to actuate said disabling means and said circuit means thereby to render said source operative and to remove said second impedance element from said cable circuit and protective means coupled to said second manually operable means and arranged to permit operation thereof solely when said control circuit is adjusted for minimum current flow from said source, said protective means including a time delay circuit ar ranged to suppress operation of said second manually operable means after operation thereof for a predetermined time interval.

5. In a terminal station for a submarine cable circuit having a repeating amplifier interposed in a portion thereof remote from said station, the combination comprising a source of direct current power for said amplifier, a control circuit coupled to said source to control the magnitude of the current delivered therefrom, a first impedance element intercoupling said source and said cable circuit, and an overcurrent protection device comprising means. selectively. to disable said source, a second impedance element, circuit means selectively to interpose said second impedance element in said cable circuit, means re,- sponsive to a flow of'current through said first impedance element in excess of a predetermined maximum value to` actuate said disabling means and said circuit means thereby to disable said source and to interpose said second impedance element in said cable circuit, first manually operable means coupled to said control circuit to adjust said control circuit for minimum current iiow from said source and second manually operable means to actuate said disabling means and said circuit means thereby to render said source operative and to remove said second impedance element from said cable circuit.

6. In a terminal station for a, submarine cable circuit having a repeating amplifier interposed in a portion thereofl remote from saidstation, said cable circuit being subjected to varying earth potentials, the combination comprising a source of direct current power for said amplier, a control circuit coupled to said source to control the magnitude of the current delivered therefrom, a rst impedance element intercoupling said source and said cable circuit, and an overcurrent protection device comprising means selectively to disable said source, circuit means selectively to protect said cable, circuit from excessive earth potentials, means responsive to a flow of current through said first impedancey element in excess of a predetermined maximum valve to actuate said disabling means and said circuit means thereby to disable said source and to protect said cable circuit from excessive earth potential, means coupled to said control circuit to adjust said control circuit for a predeterrnined` minimum current flow from said source, and

means to actuate said disabling means and said circuit means thereby to render said source operative and to suppress protection ofr said cable circuit from excessive earth potentials.

'7. In a terminal stationfor a submarine cable circuit having a repeating amplier interposed in a portion thereof remote from said station, the combination comprising a source of direct current power for said amplifier, a control circuit coupled to said source to control the magnitude of the current delivered therefrom, a rst impedance element intercoupling said source and Vsaid cable circuit, and an overcurrent protection device comprising a first relay having an operating Winding and a reset Winding, said operating Winding of said rst relay being coupled to said rst impedance element and being energized solely when the current through said nrst impedance element exceeds a predetermined value, a second relay having an operating Winding and a reset Winding, means intercoupling said first relay and the operating winding of said second relay to energize the operating winding of said second relay upon energization ofthe operating Winding of said first relay, rst circuit means selectively to disable said source, a second irnpedance element, second circuit means selectively to interpose said second impedance element in said cable circuit, an alarm circuit, means responsive. to energization of the operating winding of said second relay to operate said rst and second circuit means and to energize said alarm'circuit thereby to disable said source, to interpose said second impedance element in said cablecircuitand t provide an over-current alarm indication, first manually operable means coupled to said control circuit to adjust Vsaid control circuit for minimum current ow from said source. second manually operable meansto energize the reset Wind-` ings ofA said rst and second relays thereby to operate said rst and second circuit means and to deenergize said alarm circuit thereby to render said source operative, to remove said second impedance element from said cable circuit and to suppress said alarm indication and means coupled to said reset Winding of said second relay and to said first manually operable means to permit energization of the reset winding ofy said second relay solely when said control circuit is adjusted for minimum current ow from said source.

8. In a terminal station for a submarine cable circuit having a repeating ampliiier interposed in a portion thereof remote from said station, the combination comprising a source of direct current for said amplifier, a control circuit coupled to said source to control the magnitude of the current delivered therefrom, a first impedance element intercoupling said source and said cable circuit, and an overcurrent protection device comprising a iirst relay having an operating winding and a reset Winding, said operating Winding of said first relay being coupled to said first impedance element and being energized solely when the current through said rst impedance element exceeds a predetermined value, a second relay having an operating Winding and a reset winding, means intercoupling said first relay and the operating Winding of said second relay to energize the operating Winding of said second relay upon energization of the operating winding of said rst relay, first circuit means selectively to disablersaid source, a second impedance element, second circuit means selectively to interpose said second impedance element in said cable circuit, an alarm circuit, means responsive to energization of the operating winding of said second relay to operate said first and second circuit means and to energize said alarm circuit thereby to disable said source, to interpose said second impedance element inr said cable circuit and to provide an overcurrent alarm indication, first manually operable means coupledv to said control circuit to adjust said control circuit for minimum current now from said source, second manually operable means to energize the reset windings of said first and second relays thereby to operate said rst and second circuit means and to deenergize said alarm circuit thereby to render said source operative, to remove said second impedance element from said cable circuit and to suppress said alarm indication and protective means coupled to said reset winding of said second relayand to said first manually operable means to'permit energization of the reset winding of said second' relay solely when said control circuit is adjusted for minimum current iiow from said source, said protective means including a time delay circuit arranged to deenergize the reset Winding of said second relay a predetermined time interval after energization thereof.

9. In a terminal station for a submarine cable circuit having a repeating amplifier interposed in a portion thereof remote from said station, the combination comprising a source of direct current power for said amplifier, a control circuit coupled to said source to control the magnitude of the current delivered therefrom, a first impedance element intercoupling said source and said cable circuit, and an overcurrent protection device comprising a first relay having an operating Winding and a reset Winding, said operating Winding of said first relay being coupled to said first impedance element and being energized solely when the current through said first impedance element exceeds a predetermined value, a second relay having an operating windn ing and a reset winding, means intercoupling said first relay and the operating winding of said second relay to energize the operating winding of said second relay upon energization of the operating winding of said first relay, rst normally energized relay means selectively to disable said source, a second impedance element, a second normally energized relay means selectively to interpose said second impedance element in said cable circuit, an alarm circuit, means responsive to energization of the operating Winding of said second relay to deenergize said first and second relay means and to energize said alarm circuit thereby to disable said source, to interpose said second impedance element in said cable circuit and to provide an overcurrent alarm indication, first manually operable means coupled to said control circuit to adjust said control circuit for minimum current iiow from said source, second manually operable means to energize the reset windings of said rst and second relays thereby to energize said first and second relay means and to deenergize said alarm circuit thereby to render said source operative, to remove said second impedance element from said cable circuit and to suppress said alarm indication and protective means coupled to said reset Winding of said second relay and to said first manually operable means to permit energization of the reset Winding of said second relay solely When said control circuit is adjusted for minimum current flow from said source, said protective means including a time delay circuit arranged to deenergize the reset winding of said second relay a predetermined time interval after energization thereof.

lo. ln a terminal station for a submarine cable circuit having a repeating amplifier interposed in a portion thereof remote from said station, the combination comprising a source of direct current power for said amplifier, a control circuit coupled to said source to control the magnitude of the current delivered therefrom, a first impedance element intercoupling said source and said cable circuit, and an overcurrent protection device comprising a first relay having an operating Winding and a reset winding, said operating Winding of said first relay being coupled to said :Erst impedance element and being energized solely when the current through said iirst impedance element exceeds a predetermined value, a second relay having an operating Winding and a i winding, means intercoupling said first relay the operating Winding of said second relay to energize the operating Winding of said second relay upon energization of the operating winding of said first relay, first normally energized reiay means selectively to disable said source, a second impedance element, second normally energized relay means selectively to interpcse said second impedance element in said cable circuit, an audible alarm circuit, a visual alarm circuit, means responsive to energization of the operating Winding oi said second relay to deenergize said first and second relay means and t0 energize said alarm circuits thereby to disable said source, to interpose said second impedance element in said cable circuit and to provide visual and audible overcurrent alarm indications, first manually operable means to disable said audible alarm circuit, second manually operable means coupled to said control circuit to adjust said control circuit ior minimum current iiow from said source, third manually operable means to energize the reset windings of said iirst and second relays thereby to energize said rst and second relay means and to deenergize said alarm circuits thereby to render said source operative, to remove said second impedance element from said cable circuit and to suppress said alarm indications and protective means coupled to said reset Winding or said second relay and to said second manually operable means to permit energization of the reset winding of said second relay solely when said control circuit is adjusted for minimum current flow from said source, said protective means including a time delay circuit arranged to deenergize the reset Winding of said second relay a predetermined time interval after energization thereof.

PHILIP H. WELLS. CLIFFORD H. CRAMER.

No references cited. 

